Force sensor for surgical devices

ABSTRACT

The present disclosure relates to force sensors and force sensor substrates for use with surgical devices.

CROSS-REFERENCE TO RELATED APPLICATIONS

This application is a continuation of U.S. patent application Ser. No. 16/714,005, filed Dec. 13, 2019, now U.S. Pat. No. 11,058,506, which is a divisional of U.S. patent application Ser. No. 15/665,789, filed Aug. 1, 2017, now U.S. Pat. No. 10,595,951, which claims the benefit of and priority to U.S. Provisional Patent Application No. 62/375,012 filed Aug. 15, 2016, the entire disclosure of each of which is incorporated by reference herein.

TECHNICAL FIELD

The present disclosure relates generally to surgical devices. More particularly, the present disclosure relates to force sensors for powered surgical devices.

BACKGROUND

Force sensors are known, and there are multiple methods of fabricating these types of sensors. In one method, sensors utilize bonded strain gauges adhered to a flexing substrate within a load path. For example, a simply supported steel beam that is used integral to a load path can have a strain gauge mounted on the beam. The strain gauge is incorporated in a Wheatstone Bridge Circuit configuration and includes an excitation voltage. The circuit is designed to be at balance before deflection (i.e., no load) and the circuit will have a resistance at zero load. During loading, the beam will deflect and the strain gauge will produce a resistance change. This resistance change is a signal that can be converted into a force value imposed on the beam using a signal conditioner. Depending on the type of configuration (e.g., a quarter bridge, a half bridge, a full bridge), the signal will vary and require calibration to obtain the actual force imposed.

Some strain gauges incorporate a thin plastic film with a bonded NiCr (nickel-chromium or nichrome) wire path embedded on the film. When the film is bonded to the beam and the beam is deflected, the NiCr wire will also be subjected to bending causing a deformation of the wire. The deformation of the wire will cause the above mentioned change in electrical resistance.

The flexing substrate must be configured to elastically deform in an elastic region. In the event that the substrate is subjected to permanent deformation, the sensing wire of the strain gauge will be constrained in the deformed state. This will result in inaccurate subsequent readings of the sensor.

Solder connections are typically utilized in a strain gauge circuit, with the wire path of the strain gauge terminating at a pair of solder pads. Other connections are also used, such as laser welding, mechanical forcing of wires to the contact pads, etc.

The solder connections are subject to possible failures if the connections are made in areas of high strain. Such a strain can cause high levels of deformation causing the solder connections to fatigue. Depending on the level of strain, this fatigue can cause failure of the solder pad resulting in a loss of electrical signal rendering the sensor unusable.

If alternate sensors are used, e.g., those fabricated using vapor deposition of brittle materials, this phenomena can become more problematic. Sensor fabricated using vapor deposition include depositing several layers of media to create the sensor. Typically, the first layer consists of a thin layer of glass deposited along a surface that will incorporate the sensing wire. The sensing wire is first deposited along the substrate as a full NiCr covering. A laser then etches away the NiCr until the desired wire path is created having a plurality of solder pads forming a sensing element as described above with respect to the bonded strain gauge. Finally, a covering layer is used to prevent moisture ingress preventing shorts of the wire trace. The covering layer may be a cured epoxy or an RTV sealant (e.g., room temperature vulcanization silicone), or a vapor deposited glass with a region of glass etched away to gain access to the solder pads. This allows for the soldering of the wires or a flex cable to the sensor.

The configurations described above suffer from problems. One problem is the ability to load the substrate in an instrument. When utilizing glass along the substrate, the glass can crack when loaded. Another problem is premature failing due to large strains on the solder pads.

SUMMARY

In one aspect of the present disclosure, a force sensor substrate includes a proximal surface including a proximal load contact area, and a distal surface including at least one distal load contact area and a sensing area. The distal surface is planar and has at least one groove defined therein separating the at least one distal load contact area from the sensing area.

According to another aspect of the present disclosure, a force sensor substrate includes a proximal surface including a proximal load contact area and a distal surface including a distal load contact area and a sensing area. The distal surface is planar and has at least one groove defined in the sensing area.

Embodiments can include one or more of the following advantages:

The force sensors and substrates thereof may be configured to withstand large loading forces without disrupting the surface containing the sensing electronics (e.g., sensing elements or strain gauges, and their associated components).

The force sensors and substrates thereof may be configured to prevent tear propagation of protective conformal coatings and/or layers of sensing elements disposed thereon, and/or prevent surface micro-strain from damaging solder welds.

The force sensors and substrates thereof may be configured to withstand environmental stresses associated with autowashing and/or autoclaving, thereby rendering the force sensors more durable for reuse.

Other aspects, features, and advantages will be apparent from the description, drawings, and the claims.

BRIEF DESCRIPTION OF THE DRAWINGS

Various aspects of the present disclosure are described herein below with reference to the drawings, which are incorporated in and constitute a part of this specification, wherein:

FIG. 1 is a perspective view of a surgical device in accordance with an embodiment of the present disclosure;

FIG. 2 is a perspective view of an adapter assembly of the surgical device of FIG. 1 ;

FIGS. 3A and 3B are perspective views of a distal end portion of the adapter assembly of FIGS. 1 and 2 , with an outer sleeve of the adapter assembly removed;

FIG. 3C is an enlarged perspective view of a part of the distal end portion of FIGS. 3A and 3B;

FIG. 4A is a perspective view of a trocar connection housing disposed in the distal end portion of the adapter assembly of FIGS. 3A-3C;

FIGS. 4B and 4C are perspective views of proximal and distal surfaces, respectively, of a substrate of a force sensor disposed in the distal end portion of the adapter assembly of FIGS. 3A-3C;

FIG. 5 is a perspective view of the substrate of the force sensor of FIGS. 3A-3C, 4B, and 4C in accordance with an embodiment of the present disclosure;

FIG. 6A is a perspective view of a substrate of a force sensor in accordance with another embodiment of the present disclosure;

FIG. 6B is a close-up view of a groove defined in the substrate of FIG. 6A; and

FIGS. 7A and 7B are perspective views of the substrate of FIGS. 6A and 6B, including a flex cable and a substrate ground tab.

DETAILED DESCRIPTION

Embodiments of the present disclosure are now described in detail with reference to the drawings in which like reference numerals designate identical or corresponding elements in each of the several views. Throughout this description, the term “proximal” refers to a portion of a device, or component thereof, that is closer to a hand of a user, and the term “distal” refers to a portion of the device, or component thereof, that is farther from the hand of the user.

Turning now to FIG. 1 , a surgical device 1, in accordance with an embodiment of the present disclosure, is in the form of a powered handheld electromechanical instrument, and includes a powered handle assembly 10, an adapter assembly 20, and a tool assembly or end effector 30 including a loading unit 32 having a plurality of staples (not shown) disposed therein and an anvil assembly 34 including an anvil head 34 a and an anvil rod 34 b. The powered handle assembly 10 is configured for selective connection with the adapter assembly 20 and, in turn, the adapter assembly 20 is configured for selective connection with the end effector 30.

While described and shown as including adapter assembly 20 and end effector 30, it should be understood that a variety of different adapter assemblies and end effectors may be utilized in the surgical device of the present disclosure. For a detailed description of the structure and function of exemplary surgical devices, reference may be made to commonly owned U.S. patent application Ser. No. 14/991,157 (“the '157 application”), filed on Jan. 8, 2016, and Ser. No. 15/096,399 (“the '399 application”), filed on Apr. 12, 2016, the entire contents of each of which are incorporated herein by reference.

With continued reference to FIG. 1 , the handle assembly 10 includes a handle housing 12 housing a power-pack (not shown) configured to power and control various operations of the surgical device 1, and a plurality of actuators 14 (e.g., finger-actuated control buttons, knobs, toggles, slides, interfaces, and the like) for activating various functions of the surgical device 1. For a detailed description of an exemplary handle assembly, reference may be made to the '399 application, the entire contents of which was previously incorporated herein by reference.

Referring now to FIG. 2 , in conjunction with FIG. 1 , the adapter assembly 20 includes a proximal portion 20 a configured for operable connection to the handle assembly 10 (FIG. 1 ) and a distal portion 20 b configured for operable connection to the end effector 30 (FIG. 1 ). The adapter assembly 20 includes an outer sleeve 22, and a connector housing 24 secured to a distal end of the outer sleeve 22. The connector housing 24 is configured to releasably secure an end effector, e.g., the end effector 30 (FIG. 1 ), to the adapter assembly 20.

The adapter assembly 20 will only further be described to the extent necessary to fully disclose the aspects of the present disclosure. For detailed description of an exemplary adapter assembly, reference may be made to the '157 application, the entire contents of which was previously incorporated herein by reference.

With reference now to FIGS. 3A-3C, the adapter assembly 20 further includes a trocar assembly 26 that extends through a central aperture 101 (FIG. 4B) of a force sensor 100 and a central aperture 29 (FIG. 4A) of a trocar connection housing 28. The trocar connection housing 28 releasably secures the trocar assembly 26 relative to the outer sleeve 22 (FIG. 2 ) of the adapter assembly 20. For a detailed description of an exemplary trocar connection housing, reference may be made to U.S. patent application Ser. No. 14/865,602 (“the '602 application”), filed on Sep. 25, 2015, the entire contents of which are incorporated herein by reference.

The force sensor 100 is disposed between the trocar connection housing 28 and the connector housing 24 of the adapter assembly 20, and is configured to measure forces along a load path. As shown in FIGS. 4A and 4B, in conjunction with FIG. 3C, the trocar connection housing 28 (FIG. 4A) includes a distal surface 28 a which interfaces with, and loads a proximal surface 102 a (FIG. 4B) of a body or substrate 102 of the force sensor 100 at proximal load contact areas “Cp”. As shown in FIG. 4C, in conjunction with FIG. 3C, a proximal surface 24 a (FIG. 3C) of the connector housing 24 defines a contact surface which loads a distal surface 102 b of the substrate 102 of the force sensor 100 at distal load contact areas “Cd” (FIG. 4C). Thus, for example, as the anvil assembly 34 (FIG. 1 ) is approximated towards the loading unit 32 of the end effector 30 during clamping and/or stapling of tissue, the anvil head 34 a applies uniform pressure in the direction of arrow “A” (FIG. 3A) against the distal end 24 b of the connector housing 24 which, in turn, is transmitted to the distal load contact areas “Cd” of the force sensor 100.

As shown in FIG. 4C, the distal surface 102 b of the substrate 102 also defines a sensing area “S” onto which sensing element “Se” (shown in phantom), e.g., strain gauges, are secured. The sensing elements “Se” may be distributed on the distal surface 102 b and connected in a variety of configurations, as it within the purview of those skilled in the art.

With reference now to FIG. 5 , the distal surface 102 b of the substrate 102 is a generally planar surface having a plurality of grooves 110 defined therein. The plurality of grooves 110 provide an area of separation between the distal load contact area “Cd” and the sensing area “S” of the distal surface 102 b of the substrate 102. The plurality of grooves 110 may be micro-trenches, relief cuts, among other depressed interruptions formed in the distal surface 102 b.

The plurality of grooves 110 may have any width, depth, and/or shape that interrupts the distal surface 102 b of the substrate 102. In embodiments, the plurality of grooves 110 have a width of about 0.01 mm and a depth of about 0.01 mm. Moreover, while the plurality of grooves 110 are shown having a rectangular cross-sectional shape, it should be understood that the shape of the plurality of grooves 110 may also vary, e.g., the plurality of grooves 110 may assume a triangular, arcuate, polygonal, uniform, non-uniform, and/or tapered shape. The plurality of grooves 110 may have any size and geometry that interrupts the distal surface 102 b of the substrate 102 to allow, for example, a coating to be masked, cut, or to break without affecting the sensing area “S” of the substrate 102. In embodiments, the plurality of grooves 110 define score lines, tape lines, or break lines in the distal surface 102 b of the substrate 102 for coating(s).

The sensing area “S” of the distal surface 102 b of the substrate 102 is a flat continuous surface, and the sensing elements “Se” (FIG. 4C) are placed in large strain regions of flex in the sensing area “S.” The sensing area “S” of the substrate 102 is free of direct contact with the distal load contacting areas “Cd” via the plurality of grooves 110 thereby minimizing and/or preventing damage to the sensing element “Se” (FIG. 4C) and/or associated components thereof (e.g., layers, coatings, circuitry, solder connections, etc.) as the sensing elements and/or other associated components are not subjected to the direct loading at the distal load contact areas “Cd.”

In embodiments in which coatings are utilized to protect the circuitry and/or solder connections (not shown) disposed on the sensing area “S” of the substrate 102, the coatings may terminate at the plurality of grooves 110, without the need for masking processes, thereby minimizing or preventing tearing of the coatings in regions near the distal load contact areas “Cd” during loading of the force sensor 100.

In embodiments in which masking is desired, the plurality of grooves 110 allow for easier masking of the distal load contact areas “Cd” during fabrication of the force sensor 100. The plurality of grooves 110 provide break-away zones in which layers of the sensing elements and/or coatings thereon are forced to break thereby maintaining the integrity of the sensing area “S” of the substrate 102. In embodiments, the plurality of grooves 110 provides a region allowing for easy cutting, e.g., with a knife or razor, to separate the coating from distal load contact areas “Cd.”

Referring now to FIGS. 6A and 6B, another embodiment of a force sensor substrate 102′ is illustrated. The substrate 102′ is similar to substrate 102 and therefore described with respect to the differences therebetween.

The force sensor substrate 102′ includes a proximal surface 102 a (FIG. 4B) and a distal surface 102 b′ defining distal load contact areas “Cd” and a sensing area “S”. A groove 110′ is formed in the sensing area “S” to isolate a desired solder contact surface in the sensing area “S” to create a localized region of reduced strain. The groove 110′ includes a series of connected parallel cuts 111, each cut having a peninsula-like configuration. It should be understood, however, that one or more grooves 110′ may be formed in a variety of arrangement, e.g., different shapes, depths, and/or widths, to transfer the strain beneath the distal surface 102 b′ of the substrate 102′.

As shown in FIGS. 7A and 7B, the geometry of the groove 110′ corresponds to an end 120 a of a flex cable 120, thereby reducing the strain, under load, at the surface of solder joints (not shown) formed between the end 120 a of the flex cable 120 and the solder contact surface in the groove 110′. With the reduction of strain at distal surface 102 b′ of the substrate 102′, the integrity of the solder connections are enhanced.

While several embodiments of the disclosure have been shown in the drawings, it is not intended that the disclosure be limited thereto, as it is intended that the disclosure be as broad in scope as the art will allow and that the specification be read likewise. Any combination of the above embodiments is also envisioned and is within the scope of the appended claims. Therefore, the above description should not be construed as limiting, but merely as exemplifications of particular embodiments. Those skilled in the art will envision other modifications within the scope of the claims appended hereto. 

What is claimed is:
 1. A force sensor comprising: a substrate including a proximal surface having a proximal load contact area and a distal surface having at least one distal load contact area and a sensing area, the at least one distal load contact area and the sensing area separated by at least one relief cut defined in the distal surface, the sensing area including a groove defined therein; and at least one sensing element disposed on the sensing area of the distal surface of the substrate.
 2. The force sensor according to claim 1, wherein the groove includes a series of connected parallel cuts.
 3. The force sensor according to claim 1, wherein the at least one sensing element is a strain gauge.
 4. The force sensor according to claim 1, wherein the distal surface of the substrate is planar.
 5. The force sensor according to claim 1, wherein the substrate includes a central aperture defined therethrough, the central aperture extending through the proximal and distal surfaces.
 6. The force sensor according to claim 5, wherein the proximal load contact area is disposed adjacent to the central aperture.
 7. The force sensor according to claim 5, wherein the groove extends between the central aperture and an outer edge of the distal surface of the substrate.
 8. The force sensor according to claim 1, wherein the at least one relief cut extends around the at least one distal load contact area.
 9. The force sensor according to claim 1, wherein the at least one distal load contact area includes four distal load contact areas disposed at corners of the distal surface.
 10. The force sensor according to claim 9, wherein the at least one relief cut includes a plurality of relief cuts and each of the four distal load contact areas is separated from the sensing area by at least one of the plurality of relief cuts, each of the at least one of the plurality of relief cuts corresponding to and surrounding one of the four distal load contact areas and terminating at outer edges of the distal surface of the substrate.
 11. A force sensor assembly comprising: a force sensor including: a substrate including a proximal surface having a proximal load contact area and a distal surface having at least one distal load contact area and a sensing area, the sensing area including a groove defined therein; and at least one sensing element disposed on the sensing area of the distal surface of the substrate; and a flex cable including an end disposed within the groove of the force sensor.
 12. The force sensor assembly according to claim 11, wherein the end of the flex cable has a complementary geometry to the groove.
 13. The force sensor assembly according to claim 12, wherein the groove includes a series of connected parallel cuts.
 14. The force sensor assembly according to claim 11, wherein the end of the flex cable is soldered within the groove of the force sensor.
 15. The force sensor according to claim 1, wherein the at least one distal load contact area extends to at least one outer edge of the distal surface.
 16. The force sensor according to claim 15, wherein the at least one relief cut surrounds the at least one distal load contact area and terminates at the at least one outer edge of the distal surface of the substrate.
 17. The force sensor assembly according to claim 11, wherein the at least one sensing element is a strain gauge.
 18. The force sensor assembly according to claim 11, wherein the force sensor includes at least one relief cut.
 19. The force sensor assembly according to claim 18, wherein the at least one relief cut is defined in the distal surface of the substrate, and the at least one distal load contact area and the sensing area are separated by the at least one relief cut.
 20. The force sensor assembly according to claim 19, wherein the at least one relief cut extends around the at least one distal load contact area. 